In air-conditioning apparatuses, such as existing cooling/heating switching-type multi-air-conditioning apparatuses for buildings, at the time of cooling operation, high-pressure liquid refrigerant having flowed out of a condenser (heat source side heat exchanger) is fed into an extension pipe connecting between an outdoor unit and an indoor unit.
In an air-conditioning apparatus capable of performing cooling and heating mixed operation also, at the time of cooling operation, high-pressure liquid refrigerant having flowed out of a condenser is fed into an extension pipe (see, for example, Patent Literature 1).
Additionally, there is known an air-conditioning apparatus including a heat medium relay unit interposed between an outdoor unit and indoor units (see, for example, Patent Literature 2). In this air-conditioning apparatus, the outdoor unit and the heat medium relay unit are connected with two refrigerant pipes through which heat source side refrigerant passes, and the heat medium relay unit and each indoor unit are connected with two heat medium pipes through which a heat medium passes. In the heat medium relay unit, heat is exchanged between the heat source side refrigerant and the heat medium.
Furthermore, there is known a refrigeration cycle including a high pressure receiver with a built-in heat exchanger disposed at a condenser outlet (see, for example, Patent Literature 3). In this refrigeration cycle, high-temperature refrigerant having passed through a condenser exchanges heat with low-temperature bypass refrigerant having passed through an expansion valve in the high pressure receiver with the built-in heat exchanger to be subcooled.
Furthermore, there is known an air-conditioning apparatus including a heat source side expansion valve in a heat source unit (see, for example, Patent Literature 4). The heat source side expansion valve is provided on the liquid side of a heat source side heat exchanger, and regulates the pressure and flow rate of refrigerant.